Did anyone else notice...

How during the scene where Rose poses naked, you can see Kate Winslet touching herself right when Jack says "over on the bed--on the couch". Her hand slowly moves up and then it moves down by her side and it looks like she was doing something weird there. I keep trying to see what that was all about, but still don't understand why she did it. It's the strangest thing, but that was always one of the first things I noticed whenever I would watch that particular scene. Then again, I'm probably just a very observational person who picks up on small details like that.